Update UI when the date changes

ContentView.swift

import SwiftUI

struct ContentView: View {

    @Environment(\.scenePhase) var scenePhase
    @State private var startOfToday = Calendar.current.startOfDay(for: Date.now)
    @State private var timer: Timer?

    var dateFormatter: DateFormatter {
        let formatter = DateFormatter()
        formatter.dateStyle = .long
        formatter.timeStyle = .none
        return formatter
    }

    var body: some View {
        Text(dateFormatter.string(from: startOfToday))
            .id(startOfToday)
            .font(.title)
            .onChange(of: scenePhase) { _, newPhase in
                if newPhase == .active {
                    checkIfDateHasChanged()
                } else if newPhase == .background {
                    // Invalidate the timer when the app goes to the background
                    timer?.invalidate()
                    timer = nil
                }
            }
            .onAppear {
                startTimer()
            }
    }
    
    func checkIfDateHasChanged() {
        if startOfToday != Calendar.current.startOfDay(for: Date.now) {
            print("INFO: - Date has changed, updating UI.")
            startOfToday = Calendar.current.startOfDay(for: Date.now)
        }
    }

    func startTimer() {
        // Calculate the time interval until the next midnight
        let calendar = Calendar.current
        let now = Date()
        let nextMidnight = calendar.nextDate(after: now, matching: DateComponents(hour: 0), matchingPolicy: .strict)!
        let timeInterval = nextMidnight.timeIntervalSince(now)
        
        // Schedule a timer to fire at the next midnight
        timer = Timer.scheduledTimer(withTimeInterval: timeInterval, repeats: false) { _ in
            checkIfDateHasChanged()
            startTimer() // Restart the timer for the next midnight
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}